Distinguishing Hatchery and Wild Chum Salmon Fry with Fatty Acid Markers

Research conducted in Sapporo, Japan, has explored the use of fatty acid markers to differentiate between hatchery and wild chum salmon fry in natural environments. The study found significant differences in the fatty acid compositions of hatchery and wild fish, with levels of 18:2n-6 (linoleic acid) being higher in hatchery fish and levels of 20:5n-3 (eicosapentaenoic acid; EPA) being lower. The researchers also observed changes in the levels of these fatty acids in hatchery fish after stocking in the river, which became similar to those of wild fish by approximately 20 days.

Key Takeaways:

• The study found significant differences in the levels of 18:2n-6 (linoleic acid) and 20:5n-3 (eicosapentaenoic acid; EPA) between hatchery and wild chum salmon fry.
• Levels of 18:2n-6 were higher in hatchery fish (13.0%) than in wild fish (2.1%).
• Levels of 20:5n-3 were lower in hatchery fish (4.2%) than in wild fish (11.4%).
• The levels of 18:2n-6 and 20:5n3 in hatchery fish decreased and increased, respectively, within days after stocking in the river.
• The levels of 18:2n-6 and 20:5n3 in hatchery fish became similar to those of wild fish by approximately 20 days after stocking.

Statistics:

• 18:2n-6 levels in hatchery fish: 13.0%
• 20:5n-3 levels in hatchery fish: 4.2%
• 18:2n-6 levels in wild fish: 2.1%
• 20:5n-3 levels in wild fish: 11.4%
• Time required for hatchery fish to become similar to wild fish in fatty acid composition: approximately 20 days after stocking.

Sources:

• The Use of Fatty Acid Markers To Distinguish Hatchery and Wild Chum Salmon Fry and a Description of Post-stocking Changes In Fatty Acid Levels. Fisheries Research, 2025;291.
• Fisheries Research. Elsevier. Radarweg 29, 1043 Nx Amsterdam, Netherlands. (www.elsevier.com; www.journals.elsevier.com/fisheries-research/)
• Japan Fisheries Research and Education Agency. Salmon Res Dept, Fisheries Resources Inst, Sapporo 0620922, Japan.